From the CarMD website:
Q: Can I use CarMD to turn off my “CHECK ENGINE” light?
A: No. It is not recommended for drivers to turn off their vehicle’s “CHECK ENGINE” light until the pending or current problem has been identified and repairs confirmed. If you are a confident do-it-yourselfer or have confirmed that the “CHECK ENGINE” light is illuminated because of a loose gas gap and wish to turn it off, we recommend purchasing a product called an OBD2 code reader or scan tool from your local auto supply store.

Yes that missing feature would probably make it a no sale for me. My code reader allows erasing the codes. I suppose you could disconnect the battery and clear the codes that way if you wanted to get the online support from CarMD.